In an OFDM communication system, the transmitter performs channel coding on the transmission data, maps the channel coded data to the subcarriers, transforms the subcarriers into OFDM symbol on the time domain by means of Inverse Fast Fourier Transform (IFFT), inserts Cyclic Prefix (CP) onto each OFDM symbol, and transmits the CP-added OFDM symbol; and the receiver removes the CP, transforms the CP-removed OFDM symbol into the subcarriers on the frequency domain, de-maps the subcarriers into channel coded data, and performs channel decoding on the channel coded data to recover the transmission data.
When the receiver has a return channel in the OFDM system, the channel value is fed back per subcarrier to improve the communication efficiency. In this case, since the channel gains of the subcarriers are different from each other, the receiver is needed to use large amount of resources for feedback of the channel information about all the subcarriers, and the transmitter is needed to perform complex computation for power distribution ratio among the subcarriers by processing the feedback information.